Reactive photo acid-generating agent and heat-resistant photoresist composition with polyamide precursor

ABSTRACT

The present invention relates to a reactive photo acid-generating agent and a heat-resistant photoresist composition comprising the same. In particularly, the present invention relates to the heat-resistant photoresist composition comprising the photo acid-generating agent expressed by the following formula (1), which can increase the degree of polymerization, and polyamide oligomers having acetal or its cyclized derivatives, which have an ability of that light-exposed area is dissolved in the developer and light-unexposed area is convertible to a heat-resistant polymer in the latter heating process and thus, it can be used for passivation layer, buffer coat or layer-insulating film of the multilayer printed circuit board,  
                 
 
     wherein  
                 
 
     and R are the same as defined in the detailed description of the Invention.

BACKGROUND OF THE INVENTION Field of the Invention

[0001] The present invention relates to a reactive photo acid-generatingagent and a heat-resistant photoresist composition comprising the same.In particularly, the present invention relates to the heat-resistantphotoresist composition comprising the photo acid-generating agentexpressed by the following formula (1), which can increase the degree ofpolymerization, and polyamide oligomers having acetal or its cyclizedderivatives, which have an ability of that light-exposed area isdissolved in the developer and light-unexposed area is convertible to aheat-resistant polymer in the latter heating process and thus, it can beused for passivation layer, buffer coat or layer-insulating film of themultilayer printed circuit board,

[0002] wherein X represents —CH₂—, —O—, —S—, —SO₂—. —CO—, —NHCO—,—C(CH₃)₂—, —C(CF₃)₂—,

[0003] and R represents —CH₃, —C₂H₅, —C₃H₇, —C₄H₉, —CF₃,

[0004] Polyimide is useful for layer-insulating films of surfaceprotection layers, semiconductor dielectric, multi-layer chip module,and the like due to high stability against heat and chemicals.

[0005] Conventionally, complicated lithography processes such asphotoresist coating, prebaking, UV exposure, developing of photoresist,etching of passivation layer and removing of photoresist are requiredfor patterned heat-resistant insulating layer to make electricalconnection with the conductor wiring between upper and lower layer ormulti-layers.

[0006] Therefore, there have been intensive researches on thepreparation of direct polyimide pattern as a photosensitive compoundwith polyimides or polyamide precursors. If the heat-resistant materialshave a function of photoresist, several steps for lithographic processsuch as a photoresist coating and its removing become unnecessary inmaking via holes for wiring. Moreover, it can reduce the use of resistand chemicals. Accordingly, the use of heat-resistant photoresist cangreatly simplify and make the whole process efficient. On top of that itcan prevent the degraded resolution and reproducibility which can behappened during the process of etching and resist removal. Since whilephotoresist is generally removed out from the top of passivation layerafter lithographic processes such as light-exposure, development andetching for photoresist, the heat-resistant photoresist of the presentinvention remains in the semiconductor permanently, it provides not onlyinsulation, heat resistance, mechanical and low dielectric propertieswhich are required as semiconductor materials, but also excellentphotosensitivity, resolution, transparency and developing propertieswhich are required as photosensitive materials.

[0007] Typical examples of photosensitive chemicals are polyamic acidderivatives containing side chains bonded through ether linkage, esterlinkage, amide likicage or acid ammonium salt.

[0008] The first attempt for photosensitive polyimides was usingpolyamic acid chromate as sensitizer [Kerwin and Goldrick, Polym. Eng.Sci., 11, 426 (1971)], which was failed to be commercialized since itused an inorganic metal and the storage period was too short.

[0009] Negative photosensitive polyamides using photo-crosslinkablepolyimide precursors having esters or ionic groups as pendant groups aredisclosed in German Patent No. 2,437,348, and this system indicated thepossibility of applying polyimides in applications of semiconductorssince soluble photosensitive polyamic acid and very little amount of ametallic ion were used. However, in general the negative heat-resistantphotoresists may give us lower resolution of relief pattern due toparticles or cracks present on the photomask. Further, the resolutionmay be deteriorated by swelling of the relief pattern, since organicsolvents are used for the developer.

[0010] On the other hand, U.S. Pat. No. 4,927,736 discloses positiveheat-resistant photoresists prepared from aromatic hydroxy polyimideswith covalently attached or solution blended naphtoquinone diazide (NQ)as a photosensitive agent. Since aromatic hydroxy polyimides themselvesabsorbs large amount of light, and consequently lowering the quantumefficiency, a large amount of a photosensitive agent should be used toimprove the quantum efficiency. Besides, a large amount of polarresidues of used photosensitive agent remains in the film and polargroups such as —OHs also remain in the main chain of the polymer, andthus the dielectric constant is increased and heat-resistance isdecreased.

[0011] Other methods have been reported by introducing achemical-amplifying acid-sensitive group to aromatic hydroxy polyimides[Polymers for Advanced Technology, vol. 4, 277, 287, 1992] or polyamict-butyl ester polyimide precursors, [European Patent Publication No.0502400A1] to improve photosensitivity and resolution. In these methods,—OH or —COOH groups are blocked by a chemical-amplifying acid-sensitivegroup, thereby the solubility in aqueous alkali solutions is decreased.Then the acid produced by the photo-reaction of photo acid-generatingagent decomposes the acid-sensitive group to recover —OH or —COOH groupswhich help the polymers to be soluble in developer solutions. Eventhough the quantum efficiency can be improved by the treatments, in thecase of using aromatic polyimides containing hydroxyl group, the —OHgroups generated after the thermal treatment for curing may remain inthe film which increase the dielectric constant of the film; and in thecase of using polyamic t-butyl ester polyimide precursors, thedielectric constant is increased and the heat-resistance is decreasedbecause too much of photo acid-generating agent should be used.

SUMMARY OF THE INVENTION

[0012] The inventors have made intensive efforts to fundamentally solvethe problems of the conventional heat-resistant photoresists such as,increase of electric constant due to hydroxyl groups generated after thethermal treatment for curing, decrease of heat-resistance due to theremaining acid-generating material in the film after the development,and especially poor flatness due to the high viscosity of polymers inthe preparation of multiplayer circuit board, and to improve thephotosensitivity. As a result, inventors have discovered novel positiveheat-resistant photoresists enables of achieving high quantum efficiencythrough chemical-amplifying photosensitive agent, low dielectricconstant and high heat-resistance by minimizing the use ofphotosensitive agent and by eliminating the unreacted polar groups, andbetter flatness in the preparation of multiplayer circuit board.

[0013] Accordingly, an object of the present invention is to provide anaromatic bissulphonic diamide compound containing a photoacid-generating agent.

[0014] Another object of this invention is to provide a novelheat-resistant photoresist composition comprising polyamide oligomershaving ester groups as pendant groups and a photo acid-generating agentin an appropriate ratio to obtain advantages in minimizing post-exposurebaking process and post-exposure delay effect owing to have.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention is characterized by a photo acid-generatingagent expressed by the following formula (1),

[0016] wherein

[0017] and R are the same as defined above.

[0018] The present invention is also characterized by a positiveheat-resistant photoresist composition comprising the photoacid-generating agent expressed by the following formula (1) and thepolyamide oligomer having ester groups as pendant groups expressed bythe following formula (2),

[0019] wherein Ar₁ is a quaternary aromatic group which is selected fromthe group

[0020] Ar₂ is a secondary aromatic group which is selected from thegroup

[0021] X₁ is —CH₂—, —O—, —S—, —SO₂—. —CO—, —NHCO—, —C(CH₃)₂—, —C(CF₃)₂—,

[0022]  or

[0023] R¹ and R² are independently a hydrogen atom or C₁-C₁₀ alkylhaving

[0024] wherein R′ is a C₁-C₆ alkyl such as ethyl, propyl, isopropyl,butyl, isobutyl, t-butyl and cyclohexyl; and z is an integer of 1-4(however, excluding the case when both R¹ and R² are hydrogen atoms);

[0025] R³ and R⁴ are independently a hydrogen atom,

[0026]  which exist at the terminal portion of the molecule added toadjust the molecular weight of the oligomer;

[0027] a degree of polymerization (m+n) is 3-50; and

[0028] a polyamide oligomer is a homopolymer or a copolymer prepared bythe combination of Ar₁ and Ar₂

[0029] Hereunder is given the detailed description of the presentinvention.

[0030] A aromatic bissulphonic diamide compound according to the presentinvention expressed by the above formula (1) is a photo acid-generatingagent that generates acids by absorbing light with longer than 300 nm ofwavelength. It can improve the quantum efficiency and its amount can bereduced because it generates two equivalents of acids for a unitmolecule. Also, it helps to increase the mechanical property, since thediimide compounds formed easily through pyrolysis increases themolecular weight through imides exchange reaction with oligomers.

[0031] Accordingly, the present invention includes a heat-resistantphotoresist composition expressed by the above formula (2), whichcontains polyamide oligomer containing ester groups as pedant groups,together with the photo acid-generating agent expressed by formula (1).The content of the reactive photo acid-generating agent expressed byformula (1) is in the range of 0.3-15 wt. % to the polyamide oligomer.If too much photo acid-generating agent is used, dielectric property,mechanical property and heat resistance worsen since the molecularweight of the polymer is not sufficient, and complete holes are notformed due to the poor optical transperancy; and otherwise if too lessis used, the resolution becomes poor and mechanical strength worsens,since the acid is insufficient to function as an acid generating agent.Also, the polyamide oligomer contained in the heat-resistant photoresistcomposition of the present invention can improve planerization in thecoating process due its low molecular weight, and it can improve theheat resistance and mechanical strength since the pyrolyzed diimidereacts with polyamide acid and functions as a sensitizer.

[0032] Ester groups contained as pedant groups in polyamide oligomersexpressed by formula (2) can be carboxyl groups or acid-sensitive estershaving ethers or its cyclized derivatives. Also, a low-dielectricpolyimide film with excellent heat resistance and mechanical propertycan be prepared through the reaction of the polyamide oligomer and thephoto acid-generating agent. In additions, holes formed in thepretreatment is filled due to the reduced viscosity by the low molecularweight and the planarized coating is performed by the final heattreatment.

[0033] The following Scheme 1 is an example of the reaction of the photoacid-generating agent expressed by formula (1) and the polyamideoligomers containing esters as pedant groups expressed by formula (2),

[0034] wherein Ar₁, Ar₂, Ar₃, R, R¹, R², R³, R⁴, m and n are the same asdefined above.

[0035] As mentioned earlier, the heat-resistant photoresist compositionaccording to the present invention, obtained by mixing a polyamideoligomer and a reactive photo acid-generating agent, is treated by thefollowing process of coating, light-exposing, pre-exposure heating,developing and post-exposure baking process to provide positivephotosensitive material having low-dielectric property. Thelight-exposed area, where the heat-resistant photoresist composition ofthe present invention is coated, generates acids through a decompositionof the photo acid-generating agent. Acids transform esters of thepolyamide oligomer to the corresponding carboxylic acid, which transformfurther to polyamic acid through the acid-amplification (chain reactionof the acid) and thus the light-exposed area can be removed bydissolving in a developer. On the other hand, the light-unexposed arearemains insoluble as polyamide oligomer containg pendant ester group isnot dissolved during the development process. Bissulphonic diimidecompound containing a photo acid-generating group decomposes in thepost-heating process. So, the photo acid-generating group is volatilizedand aromatic groups are transformed into diimide monomers. Also, theester group of the polyamide oligomer containing ester group as pendantgroups is removed by overcoming the activation energy barrier. Theresultant diimide compound and polyamic acid oligomer forms thecorresponding polyimide polymer having much higher molecular weightthrough trans-imidization process. Thus, the cracking of film, which mayoccur with oligomers having low molecular weight, can be prevented sincethe mechanical strength is increased.

[0036] Namely, when a heat-resistant photoresist composition obtained bymixing a polyamide and a photo acid-generating agent is applied on thesubstrates and visible or UV light are exposed through a patterned photomask, the acid-sensitive esters are transformed to carboxyl groups.Consequently, the exposed area becomes soluble to an aqueous alkalinesolution such as tetramethylammonium hydroxide(TMAH). On the other hand,as the unexposed area to light has low solubility in an alkalinesolution, positive pattern of polyamide can be formed. Heating of thispatterned light-unexposed area converts the acid-sensitive ester groupsto carboxyl groups, and further heating causes carboxyl groups to reactwith neighboring amide groups to form imide groups which provides highheat resistance and low dielectric property.

[0037] This polyimides have a great heat resistance as to be resistantto temperature over 520° C. Besides, the acid-sensitive acetal and/orits cyclic derivative decomposes to form volatile chemicals havinglow-molecular weight (for example, ethyl vinyl ether, dihydropyran,alkyl, alkene, ether, or cyclized alkene ether derivative thereof) andnothing remains in the film. Thus, the dielectric constant becomes muchlower than that of conventional photosensitive polyimides(PSPI) usingnaphthoquinone diazide(NQ) as a photosensitizer.

[0038] Namely, ester groups are used in the present invention toheat-resistant reaction in place of hydroxyl groups, which deterioratelow-dielectric property, heat resistance and electrical property. And, alarge amount of acids is generated while photo acid-generating agent andacid-sensitive groups used for chemical amplification process aredecomposed by light or acid, and can activate decomposition ofacid-sensitive groups. Consequently, the quantum efficiency is improvedand the degree of polymerization is increased since reactive photoacid-generating agent participates in the polyimide polymerizationprocess. Thus deterioration of various properties including dielectricproperty can be minimized.

[0039] Concentration of the acid-sensitive group (—COOR¹) contained inthe polyamide oligomer expressed by formula (2) which is contained inthe heat-resistant photoresist according to the present invention is therange of 1%-90%, and preferably in the range of 15%-60%. If theconcentration of acid-sensitive group (—COOR¹) is too high, thedeveloping rate slows down, and therefore, long light-exposure time tolight or a large amount of photo acid-generating agent becomesnecessary. Otherwise, if the concentration of the acid-sensitive group(—COOR¹) is too low, there may be problems of poor resolution, decreasedthickness, and difficulty in controlling developing rate due toextremely rapid development.

[0040] The heat-resistant photoresist according to the present inventioncan be prepared in a solution state. Examples include dimethylsulfoxide,hexamethylphosphoamide, dimethylacetamide, dimethylformamide,N-methyl-2-pyrolidone, γ-butyrolactone, diglyme, butoxyethanol andpropyleneglycolmethylether acetate (PGMEA), and a small amount of thesolvent with poor solubility, such as toluene, xylene, methanol,isopropyl alcohol, may be also used. An amount of the solvent varieswith a solubility of a polyamide precursor, but its kind is not limited.However, ester-family or ether-family solvent prefers to amide-familysolvent. Also, combination of two or more of the solvents can be used toimprove the uniformity, thickness adjustment and adhesion of the film.The heat-resistantt photoresist composition is prepared in theconcentration of 10-70 wt %, and it can be adjusted according to thedesired coating thickness.

[0041] For a film formation using the heat-resistant photoresistcomposition, any one of spin coating, bar coating or doctor blademethod, which are commonly used in the electronics industry, may beused. Proper drying temperature for film formation is 40-150° C.

[0042] If the drying temperature is too low, longer drying time isrequired; and if it is too high, the transparency reduces since thedecomposition of acid-sensitive group by the pyrolysis and the formationof imide groups, which darkens color.

[0043] The proper exposure light is visible or UV with 200-500 nmwavelength, and it is more proper to use a light exposing deviceequipped with a monochrome filter in order to get better resolution andprocessibility. In the present invention, any particular equipment orlight-exposure device is not specified.

[0044] Light exposure time can be varied with experiment conditions. Inthe present invention, when a UV exposure device equipped with a 365nm-filter was used, the light exposure time could be varied from 10 secto 200 sec. If a stronger light exposure device is used, the lightexposure time can be shortened. The energy of the exposure light isdetermined with an energy meter. The resolution is determined in depthand width with a profilometer, and the cross section of the film isidentified with a scanning electronic microscope.

[0045] Polyamide oligomer used in the present invention is a well-knowncompound easily prepared by known methods. It can be prepared from anaromatic diamine and an aromatic dicarboxylic acid or its derivative asin the following Scheme 2,

[0046] wherein Ar₁, Ar₂, R¹, R², R³, R⁴, m and n are the same as definedabove.

[0047] In the above Scheme 2, the polymerization temperature isrecommended to be under 50° C., and preferably under 20° C. If thepolymerization temperature is too high, solvent-insoluble polyimide mayform due to the excessive reaction. Also, various acid-sensitive groups(—COOR¹) expressed in Scheme 2 may be included in the monopolymer orcopolymer in order to control the development rate and thephotosensitivity. For a method of bonding the acid-sensitive ester groupto the polymer, it is recommendable to use excess amount of alkyl vinylether or cyclized alkene ether derivative in the presence of an acidiccatalyst. Acid catalyst used is a strong acid such as p-toluenesulfonicacid, phosphoric acid and hydrochloric acid. The introduction ofacid-sensitive agents is preferred to perform at room temperature orbelow. If the reaction temperature is high, the pyrolysis ofacid-sensitive group and formation of polyimide may occur.

[0048] Hereunder is given more detailed description of the presentinvention by examples and preparing examples. However, they should beconstrued as limiting the scope of the present invention.

PREPARING EXAMPLE 1

[0049] After placing 12 g of 4,4′-oxydianiline (hereunder referred to as“ODA”) in a 250-mL 3-necked flask, the same was dissolved withN-methyl-2-pyrrolidinone (hereunder referred to as “NMP”). Maintainingthe temperature at 0° C., 26.62 g of4,4′-(hexafluoroisopropylidene)diphthalic acid anhydride (hereunderreferred to as “6FDA”) was added and the same was reacted while stirringfor 2 hr under N₂. After adding and dissolving 0.76 g ofp-toluenesulfonic acid in the viscous polymer solution, 10.8 g (1equivalent) of 3,4-dihydro-(2H)-pyran was added and esterified for 4 hrwhile stirring. After precipitating the reactant in a water/methanolmixture using a Waring Blender, and washing the same 3 times, it wasdried for 3 days at room temperature in vacuum to obtain a whitepolymer. Table 1 shows the viscosity of polymers obtained by varying theODA amount used in the polymerization. TABLE 1 Samples PAOF-1-1 PAOF-2-1PAOF-3-1 PAOF-4-1 PAOF-5-1 ODA 12 g 12.06 g 12.12 g 12.24 g 12.36 gamount Viscosity 0.38 0.34 0.31 0.28 0.24 (dL/g)

PREPARING EXAMPLE 2

[0050] Polyamide oligomer was prepared as in the Preparing Example 1.However, 12 g of ODA and 26.62 g of 6FDA were added and reacted for 2hr, and the addition amount of 3,4-dihydro-(2H)-pyran was changed to 2,4, 12 and 20 equivalents respectively to adjust the concentration ofacid-sensitive tetrahydropyranyl ester group. The concentration oftetrahydropyranyl ester group was determined using ¹H-NMR, and theresult is shown in Table 2. TABLE 2 PAOF- PAOF- Sample PAOF-1-1 PAOF-1-2PAOF-1-4 1-12 1-20 Equivalents of 1 equiv. 2 equiv. 4 equiv. 12 203,4-Dihydro- equiv. equiv. (2H)-pyran Concentration of 25 34 47 78 85Tetrahydro- pyranyl Ester Group (%)

PREPARING EXAMPLE 3

[0051] After placing 11.9 g of 4,4′-methyldianiline (hereunder referredto as “MDA”) in a 250-mL 3-necked flask, the same was dissolved withNMP. Maintaining a temperature at 0° C., 26.62 g of 6FDA was added andthe same was reacted while stirring for 2 hr under N₂. After adding 0.21g of ethyl carbamate, the same was stirred for 10 min. After adding anddissolving 0.76 g of p-toluenesulfonic acid in the viscous polymersolution, 40.32 g of 3,4-dihydro-(2H)-pyran was added and esterified for4 hr while stirring. After precipitating the reactant in awater/methanol mixture using a Waring Blender, and washing the same 3times, it was dried for 3 days at room temperature in vacuum to obtain awhite polymer (PAMF-1-4). Its viscosity was 0.35 dL/g.

PREPARING EXAMPLE 4

[0052] After placing 6.80 g of 1,3-phenylenediamine (hereunder referredto as “m-PD”) in a 250-mL 3-necked flask, the same was dissolved withNMP. Maintaining the temperature at 0° C., 26.62 g of 6FDA was added andthe same was reacted while stirring for 2 hr under N₂. After adding anddissolving 0.76 g of p-toluenesulfonic acid in the viscous polymersolution, 40.32 g of 3,4-dihydro-(2H)-pyran was added and esterified for4 hr while stirring. A small amount of phthalic acid anhydride was addedand the same was stirred for 10 min. After precipitating the reactant ina water/methanol mixture using a Waring Blender, and washing the same 3times, it was dried for 3 days at room temperature in vacuum to obtain awhite polymer (PAmPF-2-4). Its viscosity was 0.3 dL/g.

PREPARING EXAMPLE 5

[0053] After placing 12 g of ODA in a 250-mL 3-necked flask, the samewas dissolved with NMP. Maintaining the temperature at 0° C., 21.1 g of4.4′-(isopropylidene)diphthalic acid anhydride (hereunder referred to as6HDA) was added and the same was reacted while stirring for 2 hr underN₂. After adding and dissolving 0.76 g of p-toluenesulfonic acid in theviscous polymer solution, 40.32 g of 3,4-dihydro-(2H)-pyran was addedand esterified for 4 hr while stirring. And then, 0.48 g of ODA wasadded and the same was stirred for 10 min. After precipitating thereactant in a water/methanol mixture using, a Waring Blender, andwashing the same 3 times, it was dried for 3 days at room temperature invacuum to obtain a white polymer (PAOM-1-4). Its viscosity was 0.36dL/g.

PREPARING EXAMPLE 6

[0054] After placing 12 g of ODA in a 250-mL 3-necked flask, the samewas dissolved with NMP. Maintaining the temperature at 0° C., 26.6 g of6FDA was added and the same was reacted while stirring for 2 hr underN₂. After adding 0.48 g of ODA, the same was added for 10 min. Afteradding and dissolving 0.76 g of p-toluenesulfonic acid in the viscouspolymer solution, 34.56 g of ethyl vinyl ether was added and esterifiedfor 4 hr while stirring. And then, a small amount of phthalic acidanhydride was added and the same was stirred for 10 min. Afterprecipitating the reactant in a water/methanol mixture using a WaringBlender, and washing the same 3 times, it was dried for 3 days at roomtemperature in vacuum to obtain a white polymer (PAOFE-1-4). Itsviscosity was 0.32 dL/g.

PREPARING EXAMPLE 7

[0055] Polyamic acid oligomer was prepared as in the Preparing Example6. However, alkyl vinyl ether or cyclized alkene ether was added insteadof ethyl vinyl ether as in the following Table 3. The viscosity of theobtained polyamic acid oligomer with ester side chain is shown in Table3. TABLE 3 Inherent Amount of Viscosity Polymer Alkyl Vinyl EtherAcid-sensitive Group (dL/g) PAOFP-1-8 Propyl vinyl ether 8 mol equiv.0.32 PAOFi-1-8 Isopropyl vinyl ether 8 mol equiv. 0.35 PAOFnB-1-8n-Butyl vinyl ether 8 mol equiv. 0.33 PAOFtB-1-8 tert-Butyl vinyl ether8 mol equiv. 0.29 PAOFH-1-8 Cyclohexyl vinyl ether 8 mol equiv. 0.31PAOFF-1-4 2,3-Dihydrofuran 4 mol equiv. 0.32

EXAMPLE 1 Preparation of N,N′-Ditrifluoromethansulphonyloxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic Imide

[0056] (1) Preparation of4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:11,8′-tetracarboxylicanhydride (PODNA)

[0057] After adding 3.97 g of resorcinol and 9.92 g of potassiumcarbonate anhydride in 150 mL of dimethylformamide (Hereunder referredto as “DMF”) in a 250 mL flask equipped with a condenser and athermometer at 70° C. under N₂, 20.00 g of 4-bromo-1,8-naphtalic acidanhydride was added while stirring. After 30 min of stirring, the samewas heated to 140° C. and this temperature was maintained for 12 hr forreaction. After cooling the reaction solution, the same was precipitatedin 500 mL of iced distilled water and filtered. After washing theproduct with distilled water, the same was dried at 100° C. andrecrystallizes with DMF and extracted with {fraction (1/2)} mixture ofacetic acid anhydride and acetic acid to obtain pale-yellow4,4-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylicanhydride (PODNA) with 71% of yield.

[0058]¹H-NMR (DMSO-d₆) δ8.77 (d, 2H), 8.60 (d, 2H), 8.49 (d, 2H), 7.95(t, 2H), 7.72 (t, 1H), 7.38 (s, 1H), 7.32 (d, 2H), 7.21 (d, 2H)

[0059] FT-IR 1765,1728 cm⁻¹ (C═O) m/e: 502 (theoretical value: 502.44)

[0060] (2) Preparation ofN,N′-dihydroxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic imide (HPODNI)

[0061] After adding 2.51 g of PODNA and 0.83 g of hydroxylaminehydrochloride in 40 mL of pyridine in a 100 mL flask equipped with acondenser and a thermometer, the same was heated to 90° C. and stirredfor 2 hr. After the reaction, pyridine was distilled under reducedpressure, and the product was precipitated in distilled water, and thenfiltered. After drying the same at 100° C., 2.47 g (93%) ofN,N′-dihydroxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic imide (HPODNI) was obtained.

[0062]¹H-NMR δ10.70 (s, 2H, —OH), 8.69 (d, 2H), 8.58 (d, 2H), 8.47 (d,2H), 7.92 (t, 2H), 7.68 (t, 1H), 7.34 (s, 1H), 7.29 (d, 2H), 7.20 (d,2H)

[0063] (3) Preparation ofN,N′-ditrifluoromethanesulfonyloxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic imide (TfSPODNI)

[0064] After adding 1.00 g of HPODNI and 0.53 g of potassium carbonateanhydride in 40 mL of DMF in a 100 mL flask under N₂, the mixture wascooled to −5 to −10° C., and then 0.85 g of trifluoromethanesulfonylchloride was added slowly for 30 min. After stirring the same for 30min, the reaction was performed for 2 hr at room temperature. Afteradding 100 mL of methylene chloride, the same was washed with 2% ofsodium bicarbonate solution and distilled water, consecutively. Afterdistilling the solvent under reduced pressure, the product wasrecrystallized with a mixture of methylene chloride and hexane to obtain0.67 g (45%) ofN,N′-ditrifluoromethanesulfonyloxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylicimide (TfSPODNI).

[0065]¹H-NMR δ8.84 (d, 2H), 8.71 (d, 2H), 8.59 (d, 2H), 8.00 (t, 2H),7.70 (t, 1H), 7.43 (s, 1H), 7.36 (d, 2H), 7.26 (d, 2H)

EXAMPLE 2 Preparation of N,N′-Ditrifluoromethanesulfonyloxy-4,4′-oxydiphthalic imide (TfSODPI)

[0066] (1) Preparation of N,N′-dihydroxy -4,4′-oxydiphthalic imide(HODPI)

[0067] After adding 3.10 g of 4,4′-oxydiphthalic acid anhydride and 1.53g of hydroxylamine hydrochloride in 40 mL of pyridine in a 100 mL flaskequipped with a condenser and a thermometer under N₂, the same washeated to 90° C. and stirred for 2 hr. After distilling pyridine underreduced pressure following the reaction, the same was precipitated in 1Nof acetic acid. After filtering the same, it was washed with distilledwater and dried at 100° C. to obtain 3.23 g(95%) of N,N′-dihydroxy-4,4′-oxydiphthalic imide (HODPI).

[0068] (2) Preparation ofN,N′-ditrifluoromethanesulfonyloxy-4,4′-oxydiphthalic imide (TFSODPI)

[0069] 40 mL of DMF, 1.36 g of HODPI and 1.69 g oftrifluoromethanesulfonyl chloride was added in a 100 mL flask under N2.After cooling this mixture to −5˜10° C., 1.21 g of triethylamine wasadded slowly. After stirring the same for 30 min, the reaction wasperformed for 3hr at room temperature. After adding 100 mL of methylenechloride in the reaction mixture, the same was washed with 2% of sodiumbicarbonate solution and distilled water, consecutively. Afterdistilling the solvent under reduced pressure, the product wasrecrystallized with a mixture of methylene chloride and hexane to obtain1.69 g (70%) of N,N′-ditrifluoromethanesulfonyloxy-4,4′-oxydiphthalicimide (TfSODPI).

EXAMPLE 3 Preparation of N,N′-Ditrifluoromethanesulfonyloxy-4,4′-isopropylidenediphthalic imide (TfS-IDI)

[0070] (1) Preparation of N,N′-dihydroxy-4,4′-isopropylidenediphthalicimide (H-IDI)

[0071] After adding 3.36 g of 4,4′-isopropylidenediphthalic acidanhydride and 1.53 g of hydroxylamine hydrochloride in 40 mL of pyridinein a 100 mL flask equipped with a condenser and a thermometer under N₂,the same was heated to 90° C. and stirred for 2 hr. After the reaction,pyridine was distilled under reduced pressure, and the product wasprecipitated in 1N of acetic acid. After filtering and washing withdistilled water, the same was dried at 100° C. to obtain 3.40 g (93%) ofN,N′-dihydroxy-4,4′-isopropylidenediphthalic imide (H-IDI).

[0072] (2) Preparation ofN,N′-ditrifluoromethanesulfonyloxy-4,4′-isopropylidenediphthalic imide(TfS-IDI)

[0073] 40 mL of DMF, 1.46 g of H-IDI and 1.69 g oftrifluoromethanesulfonyl chloride were added in a 100 mL flask under N₂.After cooling this mixture to −5˜10° C., 1.21 g of triethylamine wasadded slowly. After stirring the same for 30 min, the reaction wasperformed for 3 hr at room temperature. After adding 100 mL of methylenechloride in the reaction mixture, the same was washed with 2% of sodiumbicarbonate solution and distilled water, consecutively. Afterdistilling the solvent under reduced pressure, the product wasrecrystallized with a mixture of methylene chloride and hexane to obtain1.89 g (75%) ofN,N′-ditrifluoromethanesulfonyloxy-4,4′-isopropylidenediphthalic imide(TfS-IDI).

EXAMPLE 4 Preparation of N,N′-Ditrifluoromethanesulfonyloxy-1,4,5,8-naphthalic diimide (TfSDHNI)

[0074] (1) Preparation of N,N′-dihydroxy -1,4,5,8-naphthalic diimide(DHNI)

[0075] After adding 80 mL of m-cresol and 10.00 g ofnaphthalene-1,4,5,8-tetracarboxylici dianhydride in a 250 mL flaskequipped with a condenser and a thermometer under N₂, the same washeated to 90° C. while stirring. After adding 5.56 g of hydroxylaminehydrochloride in the solution, the same was heated to 150° C. andstirred for 12 hr. After precipitating the reaction mixture in 500 mL ofmethanol and filtering the precipitate, it was recrystallized with DMFand dried at 100° C. to obtain 9.35 (84%) ofN,N′-dihydroxy-1,4,5,8-naphthalic imide (DHNI).

[0076] (2) Preparation ofN,N′-ditrifluoromethanesulfonyloxy-1,4,5,8-naphthalic diimide (TfSDHNI)

[0077] After placing 40 mL of DMF, 1.21 g of DHNI and 1.11 g ofpotassium carbonate anhydride in a 100 mL flask under N₂, this mixturewas cooled to −5 to −10° C., and 1.69 g of trifluoromethanesulfonylchloride was added slowly for 30 min. After stirring the same for 30min, the reaction was performed for 3 hr at room temperature. Afteradding 100 mL of methylene chloride in the reaction mixture, the samewas washed with 2% of sodium bicarbonate solution and distilled water,consecutively. After distilling the solvent under reduced pressure, theproduct was recrystallized with a mixture of methylene chloride andhexane to obtain 1.58 g (70%) ofN,N′-ditrifluoromethanesulfonyloxy-1,4,5,8-naphthalic imide (TfSDHNI).

EXPERIMENTAL EXAMPLE 1

[0078] After dissolving PAOF-1-4 among polyamide oligomers prepared fromPreparing Example 2, N,N′-ditrifluoromethanesulfonyloxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic imide (TfSPODNI)prepared form Example 1 as a photo acid-generating agent, andN,N′-ditrifluoromethanesulfonyloxy-4,4′-oxydiphthalic imide (TfSODPI)prepared from Example 2 in 150 mL of γ-butyrolactone with the content asin the following Table 4, the mixture was filtered through a 0.25 μmmembrane filter. After spin-coating this solution in a silicon wafer, itwas acceleration-dried at 50° C. for 5 min to obtain a insulation film.Then, UV was exposed for 30 s through photomask using a UVlight-exposing device equipped with a 365 nm filter. After heating at90° C. for 1 min, the mixture was developed in 2.38 wt % oftetramethylammonium hydroxide (TMAH) developer, and was washed withwater. This pattern-formed wafer was baked in a 350° C. oven to obtain ahardened pattern. To identify the resolution, the depth and width of thefilm was measured using a profilo meter and the cross-section wasobserved with a scanning electronic microscope. The result is shown inTable 4. TABLE 4 Residual film Heat Photo acid thickness ResolutionResistance generating agent ratio* (%) Depth Width (TGA) RemarksTfSPODNI 0.1 wt % 87% — — 525° C. No formation of pattern 1.0 wt % 85% 8μm 4 μm 529° C. — 3.0 wt % 84% 8 μm 3 μm 532° C. — 5.0 wt % 80% 8 μm 3μm 535° C. —  15 wt % 78% 7 μm 5 μm 530° C. —  30 wt % 65% — 10 μm  523°C. Partial formation of pattern on the surface TfSODPI 3.0 wt % 84% 7 μm4 μm 532° C. — 5.0 wt % 86% 8 μm 5 μm 534° C. — TfSPODNI:

TfSODPI

*residual film thickness ratio: the thickness ratio between the filmthickness after lithography and curing process and the film thicknessafter coating.

EXPERIMENTAL EXAMPLE 2

[0079] The coating solution was prepared as in Experimental Example 1,however, with different content of tetrahydropyranyl ester added aspendent group polymerized in Preparing Examples 1 and 2. Using 3 wt % ofN,N′-ditrifluoromethanesulfonyloxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic imide (TfSPODNI) prepared in Example 1 as photoacid-generating agent, dissolving, coating, drying, developing andhardening was performed with the same method as in ExperimentalExample 1. Light-exposure time was 10 s, 15 s, 110 s and 200 s,respectively. The result is shown in the following Table 5. TABLE 5Concen- tration of Residual Heat 3,4- Ex- Develop- film Resis- Dihydro-posure ing thickness Resolution tance 2H-pyran time Time ratio DepthWidth (TGA)  1 equiv.  10 sec 10 sec 80% 8 μm 3 μm 528° C.  2 equiv.  15sec 25 sec 87% 7 μm 3 μm 530° C. 12 equiv. 110 sec 15 min 85% 8 μm 5 μm534° C. 20 equiv. 200 sec  2 hr 83% 10 μm  5 μm 527° C.

EXPERIMENTAL EXAMPLE 3

[0080] The coating solution was prepared as in Experimental Example 1,however, the polymers prepared in Preparing Examples 1-3 were used.Using 3 wt % ofN,N′-ditrifluoromethanesulfonyloxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic imide (TfSPODNI) prepared in Example 1 as photoacid-generating agent, dissolving, coating, drying, developing andhardening was performed with the same method as in ExperimentalExample 1. Light-exposure time was 30 s. The result is shown in thefollowing Table 6. TABLE 6 Residual film Resolution Heat Polymerthickness ratio Depth Width Resistance PAMF-1-4 84% 9 μm 3 μm 529° C.PAmPF-2-4 85% 8 μm 3 μm 534° C. PAOM-1-4 83% 9 μm 3 μm 536° C.

EXPERIMENTAL EXAMPLE 4

[0081] The coating solution was prepared as in Experimental Example 1,however, with different content of tetrahydropyranyl ester added aspendent group polymerized in Preparing Examples 1 and 2. Using 3 wt %N,N′-ditrifluoromethanesulfonyloxy-4,4′-(phenylene-1,3-dioxy)dinaphthalene-1,8:1′,8′-tetracarboxylic imide (TfSPODNI) prepared in Example 1 as photoacid-generating agent, dissolving, coating, drying, developing andhardening was performed with the same method as in ExperimentalExample 1. Light-exposure time was 30 s. The result is shown in thefollowing Table 7. TABLE 7 Used Residual Heat Amount of film Resis-Alkyl Acid-sensitive thickness Resolution tance Vinyl Ether Group ratioDepth Width (TGA) Ethyl Vinyl 8 mol equiv. 83% 9 μm 3 μm 529° C. EtherPropyl Vinyl 8 mol equiv. 82% 8 μm 5 μm 531° C. Ether Isopropyl Vinyl 8mol equiv. 80% 8 μm 4 μm 532° C. Ether n-Butyl Vinyl 8 mol equiv. 77% 8μm 3 μm 535° C. Ether tert-Butyl 8 mol equiv. 77% 10 μm 3 μm 524° C.Vinyl Ether Cyclohexyl 8 mol equiv. 76% 10 μm 4 μm 536° C. Vinyl Ether2,3-Dihydro- 4 mol equiv. 79% 9 μm 5 μm 539° C. furan

EXPERIMENTAL EXAMPLE 5

[0082] After dissolving PAOF-1-4 among polyamide oligomers prepared fromPreparing Example 2 andN,N′-ditrifluoromethanesulfonyloxy-4,4′-isopropylidenediphthalic imide(TfS-IDI) prepared form Example 3 as a photo acid-generating agent in150 mL of γ-butyrolactone with the content as in the following Table 8,the mixture was filtered through a 0.25 μm membrane filter. Afterspin-coating this solution in a silicon wafer, it was acceleration-driedat 50° C. for 5 min to obtain a insulation film. Then, UV was exposedfor 30 s through photomask using a UV tight-exposing device equippedwith a 365 nm filter. After heating at 90° C. for 1 min, the mixture wasdeveloped in 2.38 wt % of tetramethylammonium hydroxide (TMAH)developer, and was washed with water. This pattern-formed wafer wasbaked in a 350° C. oven to obtain a hardened pattern. To identify theresolution, the depth and width of the film was measured using aprofilometer and the cross-section was observed with a scanningelectronic microscope. The result is shown in Table 8. TABLE 8 Residualfilm Resolution Heat Resistance Photo acid-generating agent thicknessratio* Depth Width (TGA) TfS-IDI 3 wt % 85% 7 μm 4 μm 537° C. 5 wt % 88%7 μm 4 μm 538° C. TfS-IDI

*residual film thickness ratio: the thickness ratio between the filmthickness after lithography and curing process and the film thicknessafter coating.

EXPERIMENTAL EXAMPLE 6

[0083] After dissolving PAOF-1-4 among polyamide polymers prepared fromPreparing Example 2 andN,N′-ditrifluoromethanesulfonyloxy-1,4,5,8-naphthalic diimide (TfSDHNI)prepared form Example 4 as a photo acid-generating agent in 150 mL ofγ-butyrolactone with the content as in the following Table 9, themixture was filtered through a 0.25 μm membrane filter. Afterspin-coating this solution in a silicon wafer, it was acceleration-driedat 50° C. for 5 min to obtain a insulation film. Then, UV was exposedfor 30 s through photomask using a UV light-exposing device equippedwith a 365 nm filter. After heating at 90° C. for 1 min, the mixture wasdeveloped in 2.38 wt % of tetramethylammonium hydroxide (TMAH)developer, and was washed with water. This pattern-formed wafer wasbaked in a 350° C. oven to obtain a hardened pattern. To identify theresolution, the depth and width of the film was measured using a profilometer and the cross-section was observed with a scanning electronicmicroscope. The result is shown in Table 9. TABLE 9 Residual film HeatPhoto acid- thickness Resolution Resistance generating agent ratio DepthWidth (TGA) Remarks TfSDHNI 0.1 wt % 88% — — 527° C. No formation ofpattern 1.0 wt % 84% 8 μm 3 μm 531° C. — 3.0 wt % 82% 8 μm 3 μm 530° C.— 5.0 wt % 82% 7 μm 3 μm 532° C. —  15 wt % 79% 8 μm 5 μm 533° C. —  30wt % 69% — 10 μm  522° C. Partial formation of pattern on the surfaceTfSDHNI:

COMPARATIVE EXAMPLE

[0084] After dissolving PamPF-2-4, which is a polyamide polymer preparedfrom Preparing Example 4, andN-trifluoromethanesulfonyloxy-1,8-naphthalimide (TfSNI) orp-nitrobenzyl-9,10-dimethoxyanthracene-2-sulfonate (NBAS) as a photoacid-generating agent in 3.0 wt % of γ-butyrolactone, the mixture wasfiltered through a 0.25 μm membrane filter. After spin-coating thissolution in a silicon wafer, it was acceleration-dried at 50° C. for 5min to obtain a insulation film. Then, UV was exposed for 30 s throughphotomask using a UV light-exposing device equipped with a 365 nmfilter. After heating at 90° C. for 1 min, the mixture was developed in2.38 wt % of tetramethylammonium hydroxide (TMAH) developer, and waswashed with water. This pattern-formed wafer was baked in a 350° C. ovento obtain a hardened pattern. To identify the resolution, the depth andwidth of the film was measured using a profilometer and thecross-section was observed with a scanning electronic microscope. Theresult is shown in Table 10. TABLE 10 Residual film Heat Photo acid-thickness Resolution Resistance generating agent ratio Depth Width (TGA)Remarks TfSNI 87% — 4 μm 523° C. Incomplete pattern formed, and crackedNBAS 85% — 4 μm 522° C. Pattern formed, but cracked TfSNI:

NBAS:

[0085] As explained above, the novel photo acid-generating agentaccording to the present invention and the heat-resistant photoresistcomposition containing polyamide oligomer having acetal or its cyclizedderivative as pendent groups can be used in any application wherelow-dielectric material is required. Especially, they are useful forpassivation layer and buffer coat of semiconductor element orlayer-insulating film of the multilayer printed circuit board.

What is claimed is:
 1. A photo acid-generating agent expressed by thefollowing formula (1),

which X represents —CH₂—, —O—, —S—, —SO₂—. —CO—, —NHCO—, —C(CH₃)₂—,—C(CF₃)₂—, or

and R represents —CH₃, —C₂H₅, —C₃H₇, —C₄H₉, —CF₃,


2. According to claim 1, wherein said photo acid-generating agentgenerates acids by absorbing light with longer wavelength than theabsorption range of polyamaide oligomer (i.e., longer than 300 nm). 3.According to claim 1, wherein said photo acid-generating agent is usedas a molecular-weight regulator.
 4. A heat-resistant photoresistcomposition comprising 0.3-15 wt. % of aromatic bis-sulphonic diimideexpressed by the following formula (1) as said photo acid-generatingagent to polyamide oligomer ester groups as pendent groups containingacetal or its cyclized derivative having expressed by the followingformula (2),

which X represents —CH₂—, —O—, —S—, —SO₂—. —CO—, —NHCO—, —C(CH₃)₂—,—C(CF₃)₂—, or

and R represents —CH₃, —C₂H₅, —C₃H₇, —C₄H₉, —CF₃,

wherein Ar₁ is a quaternary aromatic group which is selected from thegroup

Ar₂ is a secondary aromatic group which is selected from the group

R¹ and R² are independently a hydrogen atom or C₁-C₁₀ alkyl having

 wherein R′ is a C₁-C₆ alkyl such as ethyl, propyl, isopropyl, butyl,isobutyl, t-butyl and cyclohexyl; and z is an integer of 1-4 (however,excluding the case when both R¹ and R² are hydrogen atoms); R³ and R⁴are independently a hydrogen atom,

 which exist at the terminal portion of the molecule added to adjust themolecular weight of the oligomer; a degree of polymerization (m+n) is3-50; and a polyamide oligomer is a homopolymer or a copolymer preparedby the combination of Ar₁ and Ar₂.